The invention relates to a clutch arrangement, mainly for driving the tape-spindle of magnetic tape recorder and/or play-back unit, provided with three connection points and comprising an asynchronous switch-gear engaged with one of the connection points. Several clutch arrangements are already known in the field of mechanical engineering, particularly in the precision mechanics, and their variety is increasing with the emergence of new technical problems to be solved.
The book of Dr. Z. Terplan, titled "Special Clutches" (Muszaki Konyvkiado, Budapest, 1971) can be regarded as a good example for this purpose.
In the field of precision mechanics, driving the tape-spindles of tape recorders represents one of the problems requiring the use of clutch. It is commonly known, that separate driving shafts directly in contact with the tape are necessary for regulating the play-back and recording speed of the tapes. However, the normal operation the unwinding spindle has to produce braking torque, whereas the winding spindle produces tape-tensioning torque, this tightening the tape in front of and behind the driving shaft. The problem is complicated in that appropriate stretching torques, both braking and take-up, are required for quick winding even at much higher tape speeds.
In the case of recorders used for professional purposes, mainly in multi-channel data recorders or loggers, two-way actuation of the tape is necessary, consequently the same spindle performs winding and unwinding alternately. Units with three motors have come to general use in the practice, where besides the driving motor, a separately controlled motor was connected with each shaft of both spindles, and control of the motors is necessary to provide the proper operating conditions.
The use of three motors and the associated control functions increase the space requirement and the costs, therefore it is understandable that providing a single motor construction that is comparable to the three motor solution is desirable. In the sets suitable for one-way play-back, such solution have been known where the winding torque was realized with magnetic switchgear by using direct connection with the driving motor. The magnetic switchgear is suitable for transmitting appropriate torque even when significant difference exists between the speeds of the two sides connected, see Dr. Ing. Christian Scholz: "Handbuch der Magnetbandspeichertechnik" (VEB Verlag Technik, Berlin 1978, pp. 287-289).